I thought it would be clever to just use the door of the store bought cage as a little ramp into the rest of the new cage. It was ok for a few days, but Mogwai is getting bigger every day and in the last two days I've noticed that she has gotten her little foot caught on the wire between the door and the cage. It doesn't get stuck to the point that she needs help, it just trips her up. She hasn't been hurt, but it looks like she really could be. Especially when she's zooming around, she hits it hard. I'm trying to come up with something tonight to change it. If I don't find anything tonight, I'll buy her something tomorrow. Wanted to share that mistake in case any other 'new to guinea pigs' people have the same idea.